1. Field of the Invention
The invention relates to image display systems and more particularly to an image display system for improving image mura defects.
2. Description of the Related Art
High definition, low power consumption, low voltage requirements and light in weight, are all characteristics that have made liquid crystal displays (LCDs) a leading display device technology. LCDs have been broadly applicable for various applications, such as personal digital assistants (PDAs), portable computers, mobile phones, etc.
Generally, driving circuits may be integrated into LCDs to reduce costs and decrease layout area of integrated circuits. For example, driving circuits may be formed on a glass substrate of one display panel by using low temperature polycrystalline silicon thin film transistors (LTPS-TFTs). Such an LCD comprises a vertical driving circuit and a horizontal driving circuit. The former is used to select a row of display elements that are arranged in a display matrix, and the later is used to write display information into the selected row of display elements.
Moreover, the display matrix is divided into a plurality of banks. Accordingly, banks are sequentially updated by a plurality of data signals so as to decrease the data signal requirements. Conventionally, a switch is utilized to control turning-on for each bank. When a specific bank is turned on, the data signals are activated to update the specific bank. Upon the completion of updating the specific bank, the data signals further update a next bank. Therefore, it is necessary to precisely control the turning-on of each bank to avoid data for updating a current bank from being affected by those for a next bank, without inducing image mura defects.
For example, a display matrix is divided into a plurality of banks BANK_1, BANK_2, BANK_3 . . . and BANK_N, wherein each bank is controlled by switch signals S1, S2, S3 . . . and SN. FIG. 1 is a waveform diagram illustrating the overlapping of switch signals S1 and S2 for banks BANK_1 and BANK_2. As shown in FIG. 1, the switch signals S1 and S2 are overlapped. In this embodiment, when the bank BANK_1 is updated by the corresponding switch signal S1, the switch signal S2 also activates the process for updating the bank BANK_2. Therefore, the data signals for updating the bank BANK_1 are affected by the data signals controlled by the switch signal S2. The greater the overlapping of the switch signals S1 and S2, the higher the intersection level as shown in FIG. 1. As a result, the bank BANK_1 is significantly affected by the data signals for the bank BANK_2.
FIG. 2 is a display screen representation showing a display screen with different levels of overlapping switch signals. As described above, a switch signal for turning on each bank is usually generated with other corresponding signals, such as a horizontal timing signal, etc. However, due to component mismatch, temperature, or other factors, delays from the switch signals or other corresponding signals are inconsistently induced. Moreover, overlapping between the generated switch signals is not uniform and a bank problem appears in the display screen as shown in FIG. 2. As a result, the aforementioned mura phenomenon occurs and thereby deteriorates the image quality on the display screen.